CVE-2026-0203

Summary

An Improper Handling of Exceptional Conditions vulnerability in packet processing of Juniper Networks Junos OS allows an unauthenticated, network-adjacent attacker sending a specifically malformed ICMP packet to cause an FPC to crash and restart, resulting in a Denial of Service (DoS).

When an ICMP packet is received with a specifically malformed IP header value, the FPC receiving the packet crashes and restarts. Due to the specific type of malformed packet, adjacent upstream routers would not forward the packet, limiting the attack surface to adjacent networks.

This issue only affects ICMPv4. ICMPv6 is not vulnerable to this issue.

This issue does not affect AFT-based line cards such as the MPC10, MPC11, LC4800, LC9600, and MX304.

This issue affects Junos OS: 

  • all versions before 21.2R3-S9, 
  • from 21.4 before 21.4R3-S10, 
  • from 22.2 before 22.2R3-S7, 
  • from 22.3 before 22.3R3-S4, 
  • from 22.4 before 22.4R3-S5, 
  • from 23.2 before 23.2R2-S3, 
  • from 23.4 before 23.4R2-S3, 
  • from 24.2 before 24.2R1-S2, 24.2R2.

Affected Software

VendorProductVersion RangeStatus
Juniper NetworksJunos OS0 < 21.2R3-S9affected
Juniper NetworksJunos OS21.4 < 21.4R3-S10affected
Juniper NetworksJunos OS22.2 < 22.2R3-S7affected
Juniper NetworksJunos OS22.3 < 22.3R3-S4affected
Juniper NetworksJunos OS22.4 < 22.4R3-S5affected
Juniper NetworksJunos OS23.2 < 23.2R2-S3affected
Juniper NetworksJunos OS23.4 < 23.4R2-S3affected
Juniper NetworksJunos OS24.2 < 24.2R1-S2, 24.2R2affected

Weaknesses

  • CWE-755: CWE-755 Improper Handling of Exceptional Conditions

Workarounds

There are no known workarounds for this issue.

ADP Enrichment

CISA ADP Vulnrichment

  • SSVC:
  • Exploitation: none
    • Automatable: no
    • Technical Impact: partial

References